Roller blinds are generally controlled by a roller clutch assembly which is used to manually raise and lower the blind. These clutch assemblies generally consist of a housing having a barrel portion to which a roller tube support member is rotatably mounted. The blind is coupled to a roller tube which is in turn coupled to the roller tube support member. A clutch member is rotatably mounted to the barrel portion of the housing and is coupled to the roller tube support member. A looped chain is in turn coupled to the clutch member to permit the user to rotate the clutch member (and thereby the roller tube) by pulling on the chain. This permits the user to raise and/or lower the blind by simply pulling on the chain to rotate the roller tube in the desired direction. To ensure that the roller tube does not rotate without the chain being engaged, one or more lock springs are provided in the clutch assembly. These lock springs are coaxially mounted to the barrel between the barrel and the clutch member. The lock springs are configured such that engaging the chain causes the clutch member to engage the lock spring so as to slightly increase the diameter of the spring, permitting the clutch to rotate freely. The lock spring is further configured such that rotating the roller tube support alone caused the lock spring to be engaged so as to constrict the spring and lock the clutch in position.
These sorts of locking roller clutch mechanisms are very popular; however, they suffer from one serious drawback. When larger or heavier blinds are used in combination with these clutch mechanisms, the locking springs have a tendency to partially seize up, causing the clutch mechanisms to partially lock onto the barrel of the housing and resist the raising and lowering of the blinds. As a result, these clutch mechanisms do not always support the smooth and light weight operation. An improved clutch mechanism which incorporates a locking mechanism which does not stick or partially seize is therefore desirable.